Ventilation element for a storage tank

ABSTRACT

The invention relates to a storage tank ( 10 ) for receiving a medium ( 12 ) that can be frozen, in particular a reducing agent, comprising a ventilation unit ( 34, 36; 72 ) and a crucible-shaped container ( 22 ) introduced in the storage tank ( 10 ). An air chamber ( 50 ) in the crucible-shaped container ( 22 ) is connected via a ventilation line ( 60 ) or an overflow opening ( 40 ) to an air chamber ( 48 ) of the storage tank ( 10 ), which is ventilated via a ventilation unit ( 34, 36; 72 ).

BACKGROUND OF THE INVENTION

In motor vehicles with internal combustion engines, because of the more stringent exhaust gas legislation due in the coming years, amongst other things the pollutant in NOx must be reduced. One method of reducing this pollutant, which is already being used, is the SCR method (selective catalytic reaction), according to which the pollutant NOx is reduced to N₂ and H₂O with the aid of liquid reducing agent. The reducing agent is conveyed in a line from the storage tank storing the reducing agent to the metering module. The reducing agents normally used nowadays freeze between −11° C. and −40° C., depending on the antifreeze added.

In order to ensure rapid thawing of the frozen medium, an electric heater is installed in the storage tank, inside a cup open at the bottom. Thus, the heat output by the heater is used first to thaw the content of the cup. Via a suction lance, likewise of heated design, the liquid thawed around the heater is extracted via the suction lance and introduced into the exhaust gas. The conveying means regulates a constant system pressure via the pump motor rotational speed, the pressure sensor and a return flow throttle. The return flow quantity is generally led back into the heating cup again via a return line.

Because of the quantities of liquid leaving the storage tank and entering the latter, the tank interior has to be aerated and ventilated with respect to the surroundings.

SUMMARY OF THE INVENTION

According to the invention, it is proposed to ventilate the air space in the cup-shaped container via a hose line into the air space of the storage tank for receiving the reducing medium. The air space of the storage tank is connected to the surroundings via a ventilation element, by which means pressure equalization can be carried out into the surroundings, both in the air space in the cup and the air space above the tank, taking the hose line into account. The ventilation path is accordingly established from the underside of the tank via an air path, established during the heating of the return line, between the peripheral surface of the return and the inner side of the reducing agent, present in frozen form, into the upper air space in the cup, from there via the ventilation line into the air space at the upper side of the tank beside the cup-shaped container, and from there via the ventilation element into the surroundings.

The ventilation line, which extends from the air space in the upper region of the cup-shaped container into the air space of the storage tank, is preferably made of a reducing agent-resistant material such as EPDM or PA12 or the like. The ventilation line is pushed onto appropriately formed, preferably injection molded on, spigots of plastic material, both on the lid of the cup-shaped container and on the tank lid, and fixed, for example, by means of a profiled extension (Christmas tree profile).

In order to produce the fording capability of the system proposed according to the invention, it is thus merely necessary to lengthen the hose connection of the ventilation element fixed to the upper side and to connect it to a chamber permanently filled with air. This hose connection is all the more advantageous if the storage tank can be implemented as an injection molding or the tank lid of the storage tank can be made of plastic material in the course of the injection molding process. In this case, the connection, just like the spigots for pushing on the ventilation line, can all be injection molded directly onto the upper side of the tank in one operation without any complicated finishing steps being needed.

The solution proposed according to the invention offers simplification of the design and therefore greater robustness with low manufacturing costs because of the omission of a number of parts. Furthermore, in the storage tank proposed by the invention, considerable simplification of the installation can be achieved because of the reduced number of components, and thus a considerable reduction in the manufacturing costs. In relation to fording-capable systems, only one hose connection is required, which likewise results in considerable simplification.

In a further advantageous embodiment of the solution on which the invention is based, an air space which above the frozen content of a tank and an air space which above the frozen content of a cup which is introduced into the tank is aerated or ventilated into the surroundings via a separate ventilating means in each case. In this design variant of the solution proposed by the invention, in each case ventilation elements formed in the manner of tablets can be introduced into the connectors of a lid which closes the cup and into a connector for an aeration/ventilation line of the tank above an air space. By means of the two separate ventilating means provided in this design variant, ventilation of the tank and also ventilation of the cup are possible.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail below by using the drawings, in which:

FIG. 1 shows a design variant of a storage tank for receiving a reducing agent with a tank ventilating means and ventilating means for a cup-shaped container in the storage tank,

FIG. 2 shows an illustration of the fixing of a ventilation element in the lid of the cup-shaped container,

FIG. 3 shows a design variant of the solution proposed in accordance with the invention,

FIG. 4 shows a design variant of the sealing of a ventilation line, and

FIG. 5 shows a fording-capable system having a ventilation line which extends through a wet chamber into a dry chamber.

DETAILED DESCRIPTION

FIG. 1 shows that a storage tank 10 receives a reducing agent supply 12. At low outside temperatures below −11° C., the reducing agent 12 stored in the storage tank 10 begins to freeze and a solid ice phase 14 and a liquid phase 16 are established in the storage tank 10. Depending on additives which are mixed with the reducing agent supply 12, freezing of the reducing agent supply 12 in the storage tank 10 takes place at outside temperatures between −11° C. and −40° C.

The storage tank 10 comprises a tank lid 18 and a tank bottom 20 and a cup-shaped container 22 introduced into the interior of the storage tank 10 at the upper side of the storage tank 10. The cup-shaped container 22 is in turn closed via a lid 32. A heatable suction lance 24 extends through the cup-shaped container 22 and the lid 32 which closes the cup-shaped container 22. Furthermore, in the lower region of the cup-shaped container 22 there is accommodated a heater 26, which is generally operated electrically. Designation 28 designates the level of the reducing agent supply 12 in the cup-shaped container 22 and also in the interior of the storage tank 10. On the underside of the cup-shaped container 22 there is an opening 30, via which the reducing agent flows continuously into the cup-shaped container 22. The lid 32 of the cup-shaped container is fixed to a thread 34 by a lid screw fixing 54. The thread 34 is formed on an appropriately configured connector element of the tank lid 18, to which the lid screw fixing 54 for fixing the lid 32 of the cup-shaped container 22 is screwed.

The illustration according to FIG. 1 reveals that both the storage tank 10 and the cup-shaped container 22 are aerated and ventilated via a tank ventilating means 36 and a cup ventilating means 38 respectively. In order to ensure an overflow of air between an air space 48 in the storage tank 10 and an air space 50 above the level 28 of the reducing agent in the cup-shaped container 22, there is an opening 40 in the wall of the cup-shaped container 22. As the illustration according to FIG. 1 reveals, this opening 40 is closed in the event of freezing, however, since the solid phase 14 of the reducing agent 12 expands by about 10% at the liquid/solid phase transition because of the expansion of the reducing agent. Ice is deposited on the underside of the tank lid 18 and an overflow of air from the air space 48 into the air space 50 is no longer possible. For this reason, the air space 48 is ventilated via the tank ventilating means 36, while the air space 50 in the upper region of the cup-shaped container 22, which is closed by the lid 32, is aerated and ventilated separately with respect to the outside via the cup ventilating means 38.

As emerges from the illustration according to FIG. 1, both in the tank ventilating means 36 and in the cup ventilating means 38 there is a ventilation element 42, which is generally formed in the manner of a tablet.

FIG. 2 shows an illustration of the fixing of the tablet-shaped ventilation element in the ventilation connector of the cup-shaped container according to the illustration in FIG. 1.

As FIG. 2 shows, the ventilation element 42 is placed against a collar 44 in the connector of the tank ventilating means 36. In order to ensure the secure retention of the ventilation element 42 configured in the manner of a tablet underneath the collar 44, warm calking 46 may be provided, which engages under the lower flat side of the tablet-shaped ventilation element 42 and thus fixes the latter reliably underneath the opening of the connector of the cup ventilating means 38. In this way, the tablet-shaped ventilation element 42 is fixed underneath the cup ventilating means 38 via the warm calking 46. In the design variant illustrated in FIG. 1, because of the sealing point formed between the air spaces 48 and 50 in the event of freezing, two separate ventilating means, namely the tank ventilating means 36 and the cup ventilating means 38, are illustrated.

The illustration according to FIG. 3 reveals a further design variant of the solution proposed in accordance with the invention.

As FIG. 3 shows, the cup-shaped container 22 is located in the storage tank 10 for receiving the reducing agent supply 12. At low outside temperatures between −11° C. and −40° C.—depending on the addition of antifreeze agents to the reducing agent supply—phase separation of the reducing agent supply 12 into the solid ice phase 14 and into the liquid phase 16 is established both within the storage tank 10 and within the cup-shaped container 22. As a result, above the level 28 both in the cup-shaped container 22 and in the storage tank 10, the air spaces 48 and 50 already mentioned are produced. While the cup-like container 22 is closed by the lid 32, the air space 48 of the tank is closed by the tank lid 18. The two air spaces 48 and 50 are separated from each other by a sealing point 68, at which the solid ice phase 14 of the reducing agent supply 12 rests on the underside of the tank lid 18, so that the two air spaces 48 and 50 are cut off from each other and no air exchange between the latter can take place.

Formed in the lid 32 of the cup-shaped container 22 is a first connection 62 in the form of a spigot, which is used to receive a ventilation line 60. The ventilation line 60 extends from the first connection 62 on the upper side of the lid 32 which closes the cup-shaped container 22 to a second connection 64 which, for example, can be injection molded onto the upper side of the tank lid 18 in the form of a spigot. The ventilation line 60 is preferably made of a reducing agent-resistant material, preferably from a flexible elastomer material or thermoplastic. By means of the ventilation line 60, the air space 50 above the level 28 of reducing agent 12 in the cup-shaped container 22 is connected to the air space 48 in the storage tank 10 underneath the tank lid 18, i.e. ventilated into the latter. For its part, the air space 48 is assigned an aeration/ventilation line 72, which is formed in the manner of a connector, on the upper side of the tank lid 18, and closed via a spider's web screen 74. The aeration/ventilation line 72 comprises a ventilation element 42 formed in the manner of a tablet, which is fixed in and enclosed by the third spigot 70 and which is made of a water-repellent material exhibiting hydrophobic properties.

The illustration according to FIG. 3 reveals that, starting from the lower region within the cup-shaped container 22, in which the heater 26 is located, the following air path 66 is established: because of the fact that the suction lance 24 which extends through the cup-shaped container 22 is a heatable suction lance, an air gap established as a result of heating is formed between the outer side of the heatable suction lance 24 and the solid ice phase 14 of the reducing agent supply 12 enclosing said suction lance 24. Therefore, the liquid phase 16 which surrounds the heating element 26 and the air space 50 above the level 28 of the cup-shaped container 22 are connected to each other in a manner permitting pressure equalization. In accordance with the air path 66, the air space 50 is then connected to the air space 48 of the storage tank 10 underneath the tank lid 18, so that common aeration and ventilation of both air spaces, i.e. of the air space 48 and also of the air space 50, can take place via one and the same aeration/ventilation line 72 which, in the design variant according to FIG. 3, is assigned to the storage tank 10 or the air space 48 of the latter.

The lid 32 with which the cup-shaped container 22 is closed is preferably made as a plastic injection molded component, so that, advantageously, both an opening for a return 52 and the first connection 62 can be injection molded thereon. The lid 32 for closing the cup-shaped container 22 is fixed by means of a lid screw fixing 54 to an external thread 34 of the tank lid 18, which, during fabrication of the storage tank 10 as a plastic injection molded component, can likewise be produced in a simple way.

Sealing of the ventilation line 60 after being pushed onto the first connection 62 and the second connection 64 of the tank lid 18 can be implemented, for example, by means of a Christmas tree profile of the first connection 62 and the second connection 64, as illustrated in FIG. 4.

If the storage tank 10 is fabricated from plastic material as an injection molded component or in the blow-molding process, the second connection 64 and also the third connection 70, which is used to receive the connector 72 for aeration and ventilation, can advantageously be injection molded onto said storage tank 10, which has a beneficial influence on the manufacturing costs and permits a high degree of freedom with regard to the tank geometry of the storage tank 10.

Although not illustrated in the drawing of FIG. 3, there is the possibility of creating a fording-capable storage tank 10 by a hose of flexible material, for example plastic material, being connected to the third connection 70 of the aeration/ventilation line 72 on the upper side of the tank lid 18 and extending into a permanent air space, so that at all times ventilation of the air spaces 48, 50, which are connected to each other via the ventilation line 60, into the permanent air space is ensured. This possibility also exists in the design variant according to FIG. 1, in that in each case plastic hoses are slipped onto the tank ventilating means 36 and the cup ventilating means 38, and thus a fording-capable system is created.

In the design variant according to FIG. 3, a simplified structure of the storage tank 10 results, be it capable of fording, be it designed for a system not capable of fording.

The ventilation element of the cup ventilating means 38 should always be designed to be smaller than the ventilation element 42 of the tank ventilating means 36 or 72, because of the installation space and of the volume to be ventilated. In the case of the ventilation element 42 which is used in the tank ventilating means 38, dimensioning is carried out for a larger throughput of air during aeration/ventilation.

FIG. 4 shows a design variant relating to sealing off the aeration/ventilation line.

To implement effective sealing between the ventilation line 60 and the aeration/ventilating means 72 between the connections 62, 64 or a separate, third connection 70 on the lid of the storage tank 10, sealing profiled sections 76 can be applied to the connections 62, 64 and to the third connection 70 and, for example, can be formed as Christmas tree profiles. Three or more annular sections in each case extending in the peripheral direction around the end of the connections 62, 64 and 70 engage in the material of the ventilation line 60 or a ventilation hose 60 or the aeration/ventilation line 72, which extends out from the storage tank 10 in the vertical direction.

The illustration according to FIG. 5 reveals a fording-capable system having an aeration/ventilating means which extends through a wet chamber into a dry chamber.

As emerges from the illustration according to FIG. 5, the aeration and ventilation of the air space 50 in the cup-shaped container 22 is carried out via the ventilation line 60. The latter extends from the first connection 62 above the air space 50 in the cup-shaped container 22 to the second connection 64, which is connected to the air space 48 in the storage tank 10. From the air space 48 in the storage tank 10, the aeration/ventilation line 72 extends substantially in the vertical direction. As the illustration according to FIG. 5 reveals, in fording-capable systems it is necessary to ensure that the air space 48 in the storage tank 10 is always connected to the surroundings. If the entire system is located in the wet chamber 80, i.e. below a reference level 84, then it is necessary to ensure that the aeration/ventilation line 72 with ventilation elements 42 received therein extends reliably into a dry chamber 82, so that an air-carrying connection between the air space 48 in the storage tank 10 and the surroundings is always ensured. The length of the aeration/ventilation line 72 must be designed for the permissible fording depth of the vehicle, which also depends on other parameters.

The other components of the illustration according to FIG. 5 can substantially specifically be gathered from the design variant according to FIG. 3. In the design variant illustrated in FIG. 5, the cup-shaped container 22 is introduced into the storage tank 10. However, it is also possible to configure design variants in which the cup-shaped container 22 is arranged physically separately from the storage tank 10, it being possible for the cup-shaped container 22 and the storage tank 10 to be connected via the ventilation line 60 formed in the manner of a hose. From the storage tank 10, as shown in the illustration according to FIG. 5, an aeration/ventilation line 72 then extends into the dry chamber 82, depending on whether this is a fording-capable or a non-fording-capable system. It is also possible to gather from FIG. 5 that the heater 26 is fitted to the lower end of the heated suction lance 24 above the tank bottom 20 of the storage tank 10. Because of the heatable suction lance 24, the liquid phase 16 forms around the latter and, in turn, is enclosed by the solid phase 14, i.e. the frozen reducing agent supply 12.

The air space above the cup-shaped container 22 is identified by designation 50. In a manner analogous to the illustration according to FIG. 3, the overflow opening 40 between the storage tank 10 and the cup-shaped container 22 is located in the wall of the cup-shaped container 22. The tank lid 18 is identified by designation 18 in a manner analogous to the illustration in FIG. 3. 

1-10. (canceled)
 11. A storage tank (10) for receiving a medium (12) capable of freezing, having at least one aeration/ventilation line (34, 36; 72) and a cup-shaped container (22) introduced into the storage tank (10), characterized in that an air space (50) in the cup-shaped container (22) is connected via a ventilation line (60) to an air chamber (48) of the storage tank (10), which is aerated and ventilated via the at least one aeration/ventilation line (34, 36; 72).
 12. The storage tank (10) as claimed in claim 11, characterized in that a heater (26) is accommodated in the cup-shaped container (22) and a heatable suction lance (24) surrounded by the reducing agent (12) extends through the cup-shaped container (22).
 13. The storage tank (10) as claimed in claim 11, characterized in that the ventilation line (60) is made of a reducing agent-resistant elastomer.
 14. The storage tank (10) as claimed in claim 11, characterized in that the ventilation line (60) extends from a first connection (62) of a lid (32) of the cup-shaped container (22) to a second connection (64) of a tank lid (18) of the storage tank (10).
 15. The storage tank (10) as claimed in claim 14, characterized in that the first connection (62), the second connection (64) and a further connection (70) for receiving the aeration/ventilation line (72) are injection molded onto the tank lid (18) or the storage tank (10).
 16. The storage tank (10) as claimed in claim 14, characterized in that the ventilation line (60) is sealed off at the connections (62, 64) by sealing profiled sections (76).
 17. The storage tank (10) as claimed in claim 11, characterized in that the air space (48) and the air space (50) are aerated and ventilated via separate aeration/ventilation lines (34, 36) in each case.
 18. The storage tank (10) as claimed in claim 17, characterized in that the aeration/ventilation line (34, 36; 72) for constituting the fording capability comprises at least one flexible hose, which extends through a wet chamber (80) into a dry chamber (82).
 19. The storage tank (10) as claimed in claim 11, characterized in that the aeration/ventilation lines (34, 36) in each case comprise a ventilation element (42) formed in the manner of a tablet.
 20. The storage tank (10) as claimed in claim 14, characterized in that the ventilation line (60) is sealed off at the connections (62, 64) by sealing profiled sections (76), the sections having a Christmas tree profile. 